1. Field of the Invention
This invention relates generally to conveyor assemblies and, more particularly, to an idler pulley for use in a grain conveyor assembly.
2. Discussion of the Related Art
In various industries, such as those involving agriculture, manufacturing, commercial, and industrial applications it is often necessary to store and transport relatively large amounts of granular materials. In agriculture, for example, it is often necessary to store and transfer substantial quantities of grain from one location to another location. In such instances, grain conveyor assemblies are generally used to move the granular material or grain to and from storage silos or elevators at a first location to grain transportation vehicles at a second location, such as conveyors, grain transport barges, freight trains, trucks, etc.
Grain conveyor assemblies or belt conveyors generally employ a continuous conveyor belt that carries the grain on an upper surface of the conveyor belt. This continuous belt typically rides atop a set of rollers or pulleys. These pulleys include end pulleys which are used for driving the belt and intermediate pulleys which have a V-shaped contour to retain and transport the grain, via the belt. The intermediate pulleys are generally known in the art as idler pulleys because they are intermediate pulleys located between the end pulleys and are not directly driven by a drive mechanism and simply rotate under contact with the conveyor belt. Idler pulleys generally include a central cylindrical portion and opposed conically shaped or angled end portions in order to create the V-shaped contour in the conveyor belt.
Some examples of conventional idler pulleys include the idler pulley disclosed in U.S. Pat. No. 4,230,222 to Clark, which discloses a pair of parabolic shaped or angled end portions and an attached central portion to form the idler pulley. In this configuration, a pair of roller shafts are fixedly secured to the parabolic shaped end portions, via set screws that pass through a central mounting tube in which the shafts slidably engage. Inbound from the open end faces of the parabolic shaped end portions are cross spokes having a washer like ring that is secured to the mounting tube and substantially supports and transfers the load upon the roller shafts.
Another conventional idler pulley used for grain conveyor assemblies is the "Hawk" idler pulley provided by the RGF Company of Potosi, Wis. This idler pulley includes a central cylindrical portion having annular end disks which are welded to the roller shaft. Extending out from and coupled to the end disks are hollow conically shaped end portions, such that the annular end disks which are welded to the shaft are located inbound relative to the outer end faces of the conically shaped end portions.
Each of the above identified idler pulleys support a conveyor belt for retaining and transporting grain. However, each of these idler pulleys suffer from many disadvantages. For example, in the RGF idler pulley, since the roller shaft is welded to the end disks which are inbound relative to the outer end faces of the conically shaped end portions, a large shaft deflection is created by the moment arm between the bearings at the end of the shaft and the attachment of the shaft to the annular end disks. Such shaft deflection over time creates fatigue in this weld region which may cause stress fractures and potential catastrophic failure of the roller shaft. Moreover, by welding the shaft to the end disks within the idler pulley, this further causes additional stresses in this region, as well as eliminates the option of removing the shaft for maintenance or replacement purposes. Tolerance effects from the welding also creates an unbalanced and non-concentric pulley assembly.
With regard to the Clark idler pulley, the location of attachment of the shaft to the pulley is also located inbound of the end faces of the pulley, thereby also causing shaft deflection. Moreover, by utilizing set screws to secure the shafts relative to the pulley, the shaft is not substantially concentric with the rest of the pulley and a substantially unbalanced idler pulley assembly is formed. This unbalanced assembly causes vibration throughout the system. Another disadvantage with the use of set screws is that if the bearings in which the shaft rides on ever fail, there is the potential for the shaft to be forcibly rotated relative to the set screws, thereby generating extreme heat and a possible flash point for combustion of the grain dust.
Still further, in each of these designs, the end faces of the conical or parabolic shaped portions are fully open to exposure or include open spokes. This enables these areas to accumulate dust and debris, while the spokes further generate air turbulence, thereby causing or creating additional grain dust. In addition, these designs do not address the additional forces applied to the conveyor assemblies at the grain inlet portion, thereby inducing addition stresses into the system. Finally, neither of the pulleys address the speed differential associated between the cylindrical center portion of the pulleys and the conical or parabolic shaped portions of the pulleys, whereby increased friction is generated at the conical or parabolic shaped portion since this portion generally exhibits a higher velocity or speed as you move farther away from the rotating center axis. This, in turn, increases the wear on the conveyor belt, as well as induces an additional load on the drive mechanism.
What is needed then is an improved idler pulley for use in a grain and material handling conveyor assemblies which does not suffer from the above mentioned disadvantages. This will, in turn, substantially reduce shaft deflection; substantially reduce overall stress within the shaft; provide a positive balanced connection between the shaft and the pulley; provide a substantially concentric design which is easily manufactured and assembled in order to reduce overall vibration and create a more balanced design; reduce or eliminate the generation of air turbulence as the pulley rotates, thereby reducing grain or related dust; provide an idler pulley that may be readily and easily maintained over time; provide a secure positive balanced connection to the shaft which reduces possible flash points or points of extreme heat; and reduce overall friction, heat, drag and wear on the conveyor belt due to speed or velocity variances relative to the cylindrical and conical shaped portions of the pulley. It is, therefore, an object of the present invention to provide such an idler pulley for a grain conveyor assembly.